1. Field of the Invention
The present invention relates to an apparatus and a method for driving a MEMS (Micro Electro Mechanical Systems) structure and detecting the motion of the driven MEMS structure.
2. Description of the Related Art
MEMS has realized the integration of mechanical components into microelectronic elements using semiconductor processes, and promises to revolutionize numerous industrial fields including electronics, mechanics, medical, and defense industries. MEMS makes it possible to realize machines and equipments having a hyperfine structure under several μm. Especially, sensors fabricated in a hyperfine structure through MEMS technology are embedded in compact devices such as a cellular phone and detect the mechanical motion in the range of several ten nm˜several μm as an electronic signal of several pico F. The displacement of the MEMS structure is detected using the amount by which capacitance changes. A conventional apparatus for driving a MEMS structure and detecting the motion of the driven MEMS structure is described below.
FIG. 1 is a circuit diagram showing the conventional apparatus for driving a MEMS structure and detecting the motion of the driven MEMS structure. Referring to FIG. 1, the apparatus comprises a driving source 5, a first variable capacitor 6a being supplied with a driving signal from the driving source 5 to drive the MEMS structure, a second variable capacitor 6b serially connected to the first variable capacitor 6a, for detecting the motion of the MEMS structure and supplying a motion signal, and an amplifying circuit 8 connected to the second variable capacitor 6b, for outputting an amplified voltage signal Vout with respect to an input signal in a current form.
FIG. 2 is a view showing configurations of the first and the second variable capacitors 6a and 6b of FIG. 1. Referring to FIG. 2, the conventional apparatus for driving the MEMS structure and detecting the motion of the driven MEMS structure comprises a first fixed electrode plate 11a supplied with the driving signal, a second fixed electrode plate 11b disposed apart from the first fixed electrode plate 11b by a predetermined distance and opposite to the first fixed electrode plate 11b, and a movable electrode plate 15 integrally formed with the MEMS structure 14, which is supported on a spring 12 and a damper 13 to be movable to a predetermined direction, and located between the first an second fixed electrode plates 11a and 11b. The first variable capacitor 6a is embodied by the first fixed electrode plate 11a and the movable electrode plate 15, and the second variable capacitor 6b is embodied by the movable electrode plate 15 and the second fixed electrode plate 11b. 
In the conventional driving of the MEMS structure and detecting of the motion of the driven MEMS structure, it is necessary to comprise a driving electrode for driving the MEMS structure 14 and a detecting electrode for detecting the motion of the MEMS structure 14, separately. Due to the addition of the detecting electrode which does not contribute to the driving of the MEMS structure 14, a problem of volume increase is created in the system that is required to be small-sized.